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Coolant sensor woes. '91 5.7 TBI

So I found out the coolant sensor on top by the thermostat housing is bad via a ohms test. I have a copy of ALLDATA and I then come across a connector image. It shows (#3) the one on top everyone knows about and its called "coolant temperature sensor". the other (#19) is called "Engine coolant Sensor".

I can not find a diagram of BOTH circuits. only the one on top. If there are two I want to verify the other is functioning as well. My gauge in cab has been showing cold for some time. Like I said the sensor on top is in fact bad Ohms are all over the place and the engines runs like crap when not plugged in.

I just came across this exploded connector view a little bit ago and I know there is a sensor there as I just saw it when I was testing today. Its between #1 and #2 cylinder and is a single green wire. Is the single wire sensor (#19) be the gauge unit? and the #3 on top just for the ECM? This is what I am starting to getting out of it. Any light shed on this would be great.

This whole thing started because engine seemed to be running cold a lot lately and mpg is down, found sendor on top bad now wanting to test or replace other unit (if it is that). Going to be doing a new thermostat as as well and checking clutch on fan.

On my 94 TBI 350 the sensor for the temperature gauge only is the one in the head between cylinders 1 & 3.
The sensor up on the intake manifold lets the PCM know what the engine temperature is, when you unplug that sensor it sets a fault code and the engine goes into limp home mode (and runs rough).
From memory the sensors have different part numbers and a different number of pins.